This invention relates generally to the field of concrete depression form systems and methods utilized to create a poured concrete slab having a first upper surface and a depressed second upper surface, the second upper surface being lower than the first upper surface.
In the construction of multi-floor apartment buildings, commercial buildings and the like, it is often desired to provide upper floors with peripheral exterior concrete slabs, such as decks or walkways, which are exposed to the elements. To prevent rain water from flowing into the interior of the building, it is customary to construct the exterior portion of the slab with a depressed or lower upper surface relative to the interior floor portion of the slab, such that the vertical wall or shoulder resulting from the difference in height between the interior slab portion upper surface and the exterior slab portion upper surface acts as a water stop or dam.
Both the primary interior concrete slab portion and the depressed exterior concrete slab portion in such a construction may be poured simultaneously by utilizing a horizontally extending, elongated depression rail or scrim that is mounted on individual spaced supports placed upon the bottom form surface, the bottom form often comprising plywood panels which are removed after the concrete cures. The upper edge of the rail is positioned at the desired height for the upper surface of the interior concrete slab portion. The lower edge of the rail is positioned at the desired height for the upper surface of the depressed exterior slab portion, such that the height of the rail determines the height of the water stop wall. When the concrete is poured it first flows under the rail to create the exterior depressed slab portion. The depression rail then impedes additional flow while the pour continues so as to fill in the interior slab portion to the desired height.
The most common technique utilized in this method has not changed in many years. It is typical to use wooden boards, such as 2×4's, as rails mounted upon wooden, plastic or metal supports. This technique is very labor intensive and requires experienced workers to provide a proper set-up prior to the concrete pour. Wooden supports must be removed from the slab prior to complete hardening, with the resulting wells in the slab having to be filled in later. Typical designs for plastic or metal supports usually require post-curing processes, such as cutting or grinding, to remove exposed portions of the supports. It is also known to utilize sacrificial or consumable rails and supports where both remain embedded within the concrete slab, such as shown in U.S. Pat. No. 4,466,222 to Mitchell.
It is an object of this invention to provide a concrete depression form system and method that provides for easier installation than known systems, wherein the rail is readily removable from sacrificial support towers after the concrete has sufficiently cured, leaving a slab having an elevated interior slab surface and a depressed or lower exterior slab surface, the support towers being structured such that concrete flow is only minimally impeded and such that no portion of the support towers extends outward from the slab surfaces, securement of the support towers to the base is readily accomplished, and wherein post-curing processing of the support towers is not required. It is a further object to provide such a system and method possessing other advantages over known systems and methods, as will be apparent from the following disclosure.